Magnaporthe oryzae causes rice blast disease, but little is known about the dynamic restructuring of the actin cytoskeleton during its polarized tip growth and pathogenesis. Here, we used super-resolution live-cell imaging to investigate the dynamic organization of the actin cytoskeleton in M. oryzae during hyphal tip growth and pathogenesis. We observed a dense actin network at the apical region of the hyphae and actin filaments originating from the Spitzenkörper (Spk, the organizing center for hyphal growth and development) that formed branched actin bundles radiating to the cell membrane. The actin cross-linking protein Fimbrin (MoFim1) helps organize this actin distribution. MoFim1 localizes to the actin at the subapical collar, the actin bundles, and actin at the Spk. Knockout of MoFim1 resulted in impaired Spk maintenance and reduced actin bundle formation, preventing polar growth, vesicle transport, and the expansion of hyphae in plant cells. Finally, transgenic rice (Oryza sativa) expressing RNA hairpins targeting MoFim1 exhibited improved resistance to M. oryzae infection, indicating that MoFim1 represents an excellent candidate for M. oryzae control. These results reveal the dynamics of actin assembly in M. oryzae during hyphal tip development and pathogenesis, and they suggest a mechanism in which MoFim1 organizes such actin networks.

稻瘟病菌引起稻瘟病，但人们对肌动蛋白细胞骨架在其极化尖端生长和发病机制过程中的动态重组知之甚少。在这里，我们使用超分辨率活细胞成像来研究M中肌动蛋白细胞骨架的动态组织。 oryzae菌丝尖端生长和发病机制。我们在菌丝顶端区域观察到密集的肌动蛋白网络，肌动蛋白丝源自 Spitzenkörper（Spk，菌丝生长和发育的组织中心），形成辐射到细胞膜的分支肌动蛋白束。肌动蛋白交联蛋白 Fimbrin (MoFim1) 有助于组织肌动蛋白分布。 MoFim1 定位于心尖下环处的肌动蛋白、肌动蛋白束和 Spk 处的肌动蛋白。 MoFim1的敲除会导致 Spk 维持受损并减少肌动蛋白束形成，从而阻止植物细胞中的极性生长、囊泡运输和菌丝扩张。最后，表达针对MoFim1的 RNA 发夹的转基因水稻 ( Oryza sativa ) 表现出改善的M抗性。米曲霉感染，表明MoFim1是米曲霉的绝佳候选者。稻瘟病防治。这些结果揭示了M中肌动蛋白组装的动态。他们提出了MoFim1 组织此类肌动蛋白网络的机制。